The black walnut is an Ontario native, prized for its timber as well as for nuts. Large 150 year old specimen trees have been sold for veneer for thousands of dollars. It is important to get assistance from the Ministry of Natural Resources when considering the sale of valuable trees. Black walnut timber plantations are routinely established in the fertile Southern Ontario lowlands.

The black walnut is one of the most successful edible nut trees in Ontario. It is well adapted to our winter cold, and unlike Persian walnuts, avoids late spring frosts by delaying leafing by 2 weeks later than other introduced Juglans species in the spring. As a result it is suited for much of Southern Ontario. Plantings and wild trees can be found from Windsor in the south-west to Ottawa in the east. There are even black walnut trees thriving in Quebec City east of that. A strain of black walnut has even adapted itself to the rigors of the dry fertile prairies (zone 3) of Manitoba.

More limiting than climate is the soil type and drainage conditions. Black walnut succeeds well beyond its native range, wherever pH readings are between 6 and 7. Eroded limestone soils ranging from sand to clay are ideal. They are at home along the whole length of the eroded edge of the Bruce Trail (Niagara escarpment to the Bruce Peninsula). Deep well-drained soils are important to proper development and growth.

28 year old "Emma K" Black Walnut

Though the black walnut is well established in Ontario, the crop of delicious nuts it produces has not been utilized except by a few persistent foragers. The early pioneers highly valued the rich tasting nuts and put away many sacks of them each year. Each farmstead had its orchard of fruit and nut trees to provide it with its source of winter food. That all but disappeared when easier cracking Persian walnuts became common in the grocery stores. With modern tree shakers, harvesters, nut hullers, crackers and sorting machines being available, it is possible to profit from the nut crop again. The industry is alive and well in Stockton, Missouri where millions of pounds of black walnuts are processed each year. Nuts are collected from all of the surrounding states for processing. The total kernel crop is marketed domestically. Almost none is left over for export. Not only do they sell the nut meats but they also have a robust market for the shells that have important uses in sandblasting and oil well drilling.

With modern tools, equipment and robotics, we have an opportunity to simplify and make the processing of black walnut a reality in Ontario.

Though the black walnut industry is based on wild trees in North America, many selections have been found that offer larger nut meats in easier cracking shells. A few of the cultivars that do well in Southern Ontario include: Emma K, Thomas, Sparks 147, Weschcke and Bicentennial.

Grower Considerations

The black walnut aphid can be a serious pest on black walnut in some areas where natural predators are scarce. The honeydew produced by the aphid blackens and stains everything under it with sticky goo. This has little effect on the nuts but homeowners don't appreciate this and regard it as a poor yard tree.

The walnut husk fly is a minor concern with black walnut, where it can cause a disaster to Persian walnut crops. The fly lays its eggs in the husk of the nut and the larvae burrow into the husk turning it black in spots. If the nuts are hulled quickly after harvest, the larvae do no harm to the nut meat that is well protected by the thick shell.

The greatest concern looming into the future is the "thousand canker disease". This disease is the result of the combined activity of a fungus (Geosmithia morbida) and the walnut twig beetle (Pityophthorus juglandis). The beetle carries the fungus in its tunnels that it creates in the trunk and branches of the black walnut tree. It is the fungus that causes the greatest damage that eventually kills the tree. This is a disease of the western states in the USA. In the west it is a minor pest only affecting side branches and seldom killing trees. Persian walnut and heartnut are not affected. It is believed that the transport of firewood from the west introduced this pest to the east. It was first reported in Tennessee in 2010. Surveys were conducted and it was then discovered in Pennsylvania and Virginia in 2011. Since then it was found in Indiana, Maryland and North Carolina. Quarantines and further monitoring of the spread of this disease is all that can be done. So far this disease has not been found in Ontario.